Unexpected Li2O2 Film Growth on Carbon Nanotube Electrodes with CeO2 Nanoparticles in Li–O2 Batteries

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• 作者：Chunzhen Yang ; Raymond A. Wong ; Misun Hong ; Keisuke Yamanaka ; Toshiaki Ohta ; Hye Ryung Byon
• 刊名：Nano Letters
• 出版年：2016
• 出版时间：May 11, 2016
• 年：2016
• 卷：16
• 期：5
• 页码：2969-2974
• 全文大小：524K
• 年卷期：0
• ISSN：1530-6992

文摘

In lithium–oxygen (Li–O₂) batteries, it is believed that lithium peroxide (Li₂O₂) electrochemically forms thin films with thicknesses less than 10 nm resulting in capacity restrictions due to limitations in charge transport. Here we show unexpected Li₂O₂ film growth with thicknesses of ∼60 nm on a three-dimensional carbon nanotube (CNT) electrode incorporated with cerium dioxide (ceria) nanoparticles (CeO₂ NPs). The CeO₂ NPs favor Li₂O₂ surface nucleation owing to their strong binding toward reactive oxygen species (e.g., O₂ and LiO₂). The subsequent film growth results in thicknesses of ∼40 nm (at cutoff potential of 2.2 V vs Li/Li⁺), which further increases up to ∼60 nm with the addition of trace amounts of H₂O that enhances the solution free energy. This suggests the involvement of solvated superoxide species (LiO₂(sol)) that precipitates on the existing Li₂O₂ films to form thicker films via disproportionation. By comparing toroidal Li₂O₂ formed solely from LiO₂(sol), the thick Li₂O₂ films formed from surface-mediated nucleation/thin-film growth following by LiO₂(sol) deposition provides the benefits of higher reversibility and rapid surface decomposition during recharge.